Answer:
39 cups
Step-by-step explanation:
If we assume that the 3.5 cups of concentrate make 3.5+3 = 6.5 cups of tea, we can use the proportion ...
6.5/3.5 = x/21
to find the x cups of tea Ahab can make with 21 cups of concentrate.
Multiplying by 21, we get ...
x = 21(6.5/3.5) = 39
Ahab can make 39 cups of tea.